Shoulder belt issue on 68 Barracuda

Cut a slot just big enough to slip a nut through in the upper portion of that section . Then tape the nut to a Q-tip or such and carefully slide the nut in and start threading it in carefully... once it is started you can yank the Qtip away from nut and use a needlenose or someting to hold nut while tightening the bolt...
The headliner will be the biggest hurdle...